Semperflorens begonias, commonly called wax begonias, are one of the most popular bedding plants in the Western world. Innumerable flats of these sturdy plants are poked into the soil every spring to create lush beds of flowers. The reasons for this heavy use are obvious—they're a durable, ever-blooming plant that provides sweeping color in single or double blooms.
While most people think of these exclusively as outdoor plants, in reality, they also make excellent indoor plants. Wax begonias are not merely annuals. In reality, they are a perennial shrub that grows to respectable size and flowers readily.
Growing Conditions for Wax Begonias (Semperflorens)
These are sturdy plants that will do best under these conditions:
Wax begonias can grow in full sun in all but the hottest and harshest climates. Give them as much bright light as possible.
Water when the soil dries through the first half-inch, then water thoroughly and let drain. Established plants also require less water and can go for a long time between waterings. When you do water, make sure it's a thorough watering, then let the pot drain completely. Do not let them sit in water, which encourages root rot. They benefit from relatively lower humidity. Semperflorens should not be sprayed or subjected to especially high humidity as it will encourage powdery mildew on their leaves.
They like it average to warm. As with all begonias, they do not like cold drafts and cannot tolerate freezing, but will thrive with temperatures in the 60s.
They prefer airy, light, fast-draining soil.
Use liquid fertilizer weekly at quarter strength or biweekly at half strength. Every third or fourth feeding, use a high phosphorous fertilizer.
Wax begonias are almost exclusively F1 hybrids produced by large nurseries in huge quantities. These plants will not produce accurately from seed, but like many other begonias, they propagate easily from leaf-tip cuttings. Take cuttings without blooms but at least two nodes and bury them in the moist potting soil mix, then leave in a warm, semi-shaded spot until new growth appears. The best time to take cuttings is in the spring when the plants begin to grow again.
Wax begonias happily grow into small shrubs if allowed to, reaching a maximum height of about 18 inches, depending on the cultivar and species. Like other begonias, they thrive when they are slightly pot-bound, so it's likely that a wax begonia will only need to be repotted once or perhaps twice in its life. In most cases, it's better to take cuttings of older plants than to struggle with repotting and rehabilitating leggy specimens. If you are repotting, do it in the spring into a slightly larger pot with fresh, fast-draining and richly organic potting soil.
Varieties of Wax Begonias
Today, almost all plants known as wax begonias are hybrids produced from the same few ancestors. The basic ancestor is the B. cucullata, which was once called the B. semperflorens. This plant has been bred extensively over the years and its many descendants are correctly known as the Semperflorens cultorum group. The physical characteristics of these plants depend on the breeder, but they have been hybridized for various colors and heights. The B. schmidtiana is also included in the semperflorens group. According to the American Begonia Society, this is a many-branched plant with small velvety leaves.
Semperflorens begonias, or wax begonias, are not difficult plants to grow and can be included in a massed windowsill planting for bright indoor color. To keep the plants looking vibrant, pinch off old blooms and keep the plant free of brown and old leaves.